1. Field of the Invention
The present invention relates to an angular velocity sensor using piezoelectric vibration, in particular, an angular velocity sensor using a quartz substrate.
2. Description of the Related Art
Angular velocity sensors are used for camera shake detection in photographic devices, direction detection in car navigation systems, and so on. In recent years, such a demand prevails in various fields, and sensors are required to have improvement in performance and be downsized.
As an angular velocity sensor using a piezoelectric substrate, an angular velocity sensor with a piezoelectric vibration system using two vibration modes of an excitation mode and a detection mode orthogonalized has been known. For example, U.S. Pat. No. 5,396,144 discloses an angular velocity sensor using a tuning-fork crystal resonator performing flexural vibration in the specification. Such an angular velocity sensor using flexural vibration tends to easily have degradation of characteristics due to a support of a resonator. The related art has a structure provided with a suspension system on a support portion so as to avoid influence on the support portion from the outside world.
Further, Vibratory Gyroscope Using Trapped-Energy Vibrators of Y-cut LiTaO3(Nakamura et al.), IEEE ULTRASONICS SYMPOSIUM, pp. 611-614, 2001 discloses an angular velocity sensor utilizing a thickness-shear resonator with a LiTaO3 substrate. Thickness-shear vibration is an energy trapping type. Therefore, by using this vibration, a supporting structure of a resonator is facilitated since a support of the resonator does not affect on the vibration.
Such an angular velocity sensor using flexural vibration while not receiving impact from a support portion on resonator characteristics causes a problem in which a structure of the support portion becomes complicated. Further, a conventional angular velocity sensor using thickness-shear vibration has a simple supporting structure of a resonator. However, since a LiTaO3 substrate is used, stable frequency-temperature characteristics are not obtained. Therefore, the conventional angular velocity sensor has a problem in which highly accurate detection of angular velocity cannot stably provide in a wide range of temperature.